The present invention relates to a driving condition control method and system installed in a vehicle, which are capable of controlling the driving conditions of the vehicle.
Conventional driving condition control systems have been created, one of which is disclosed in Japanese Unexamined Patent Publication No. H08-207542, and another one of which disclosed in Japanese Granted Patent Publication No. 3116686.
The driving condition control system disclosed in the former publication, when the vehicle runs over a road surface and a yaw sensor attached to the front portion of the vehicle body senses large amount of yaw moment, determines that the vehicle is experiencing understeer. The understeer means that a condition where the front of the vehicle tends to break out and slide toward the outside of an intended turn.
On the other hand, when a yaw sensor attached to the rear portion of the vehicle body senses large amount of yaw moment, the driving condition control apparatus determines that the vehicle is experiencing oversteer. The oversteer means that a condition in cornering when the rear wheels of a vehicle tend to break loose and slide outward so that the front turns the inside of an intended turn.
The driving condition control apparatus performs a front-rear torque distribution control for restraining the oversteer or the understeer, and/or performs a steering control for avoiding the oversteer or the understeer.
Moreover, the driving condition control apparatus disclosed in the later publication is equipped with a variable torque transmission. When the vehicle runs over the road surface, the variable torque transmission distributes torque between the right and left wheels on at least one of the axel to be satisfied with the driver's steering angle, the running speed of the vehicle, and so on.
The apparatus disclosed in the former publication controls the driving conditions of the vehicle according to the amount of yaw moment. It is noted that the yaw moment indicates angular motion of the vehicle body about vertical axis through its center of gravity. The angular motion of the vehicle body is caused after the driving torque produced by the engine is transmitted to the wheels so that the tires are subjected to traction force from the road surface.
That is, the apparatus disclosed in the former publication only carries out the driving condition control after the yaw moment of the vehicle body is produced, which may delay the detection of the vehicle's driving conditions.
The apparatus disclosed in the later publication only performs the torque distribution so that it is difficult to rapidly detect that the vehicle's driving conditions are different from driver's intended driving conditions.